1. Field of the Invention
The device provides a satisfactory solution for the physical separation of ions dissolved in an aqueous solution from the water molecules of said solution. It has been designed, basically, for the desalination of seawater.
2. Description of the Related Art
The background on selective-membrane desalination devices refers to machines or units that separate the ions dissolved in an aqueous solution using an electrical potential between two electrodes connected to an external power source, i.e. based on electrodialysis. Our desalinisation device does not include electrodes for generating said potential. Thus, it is not based on current concepts of saltwater electrodialysis.
U.S. patent publication No. 2004/0262234 discloses an apparatus and method for the purification of fluids and Applicants believe it is the nearest reference to our selective-membrane and magnetic-field desalinisation invention that does not use electrodes. It uses a rotating magnetic field and ion-selective-membrane batteries; however, there is still at least one channel that is rich in anions and another channel that is rich in cations, which generate an electrical potential. This does not occur in the present invention that is being claimed.
Applicants are aware of the existence of the Spanish utility models published under numbers 1066215 (ion-selective-membrane and magnetic-field desalination device according to electrical charge) and 1067217 (desalination device by rotation of a magnetic field and selective membranes according to their electrical charge). Both documents describe devices that desalinate part of a seawater flow based on the layout of a magnetic field, obtaining separate product and reject water currents in different channels; however, in both cases, the proposed objective was achieved by means of a channel structure in which one channel was filled only with positive ions and another channel was filled only with negative ions (the end channels), whereas the central channels remain neutral owing to the fact that they were filled or drained with the same number of positive and negative ions. The end channel that is filled with positive ions created a positive potential. The other channel, at the other end, which is filled only with negative ions, creates a negative potential. Accordingly, the difference in potential creates an electrical field that has a negative effect on the objective being sought, since the electrical forces that are created oppose the forces of the magnetic field, inhibiting the movement of the ions and, therefore, hindering their stratification into channels of dilute and concentrate
As a result, a pair of electrodes connected together by an external conducting wire is necessary to close the electrical circuit. When said circuit is closed, the potentials cause the appearance of a movement of electrons. In turn, these electrons cause redox reactions at the ends. The result of these redox reactions is that the end channels are neutralised and the electrical potential at the ends disappears (to a large extent, there is always a remaining charge that causes the movement of electrons).
The special configuration of the device that is being advocated, which has no end channels that generate potentials, eliminates the electrical forces that counter the Lorentz forces created on the ions by the magnetic field, so that the movement of ions can continue without the need for the electrodes and with the advantage of avoiding the appearance of redox reactions. Furthermore, the energy that was used in the devices described in the utility models to create an electrical potential that generated electron movement, thus minimising the electrical field, is no longer necessary since said energy was used to neutralise the potential at the ends, but not in the useful movement of the ions. This represents a significant reduction of device-operation costs and a considerable improvement in performance.
Applicants are not aware of any similar device for carrying out the aforementioned water desalinisation work, which makes the novelty of this invention evident as it will provide a good number of benefits for the saltwater desalination industry and for the use of said water.
The present application also discloses improvements for increasing water production levels, energy performance levels and the effectiveness of the device, whereby they focus on the following specific issues:                On the one hand, the inclusion of the option for making the parts of the device in prismatic geometries instead of cylindrical geometries as mentioned in the main patent.        On the other, the determination of the required separation between the membranes inside the chamber to obtain the highest possible level of performance of the device.        Finally, it includes the option of achieving the magnetic field that is necessary to generate the movement of ions through the layout of superconductor coils through which an electrical current will flow.        
The device bases its operation on the absence of end chambers. Accordingly, all the channels are maintained electrically neutral, thus avoiding the generation of potentials that have a negative effect on the desalination process. This configuration suggested a cylindrical model with all the bodies mounted on a common axle. The substitution of the original cylindrical geometry by prismatic geometry brings new options for the operation of the device, also enabling the manufacture of these elements.
In addition, the separation between membranes is a very important parameter when determining the energy performance levels of the system and the Donnan potential is a factor of great relevance. In one single channel, the ion concentration will not be consistent, since, owing to the attraction of the free ions in the selective membranes, there are higher levels of concentration in the nearby areas.
The highest concentration of ions in the areas near these membranes will therefore generate a small electrical potential (Donnan potential) that will hinder the movement of the ions caused by the magnetic field. As this circumstance cannot be eliminated, setting an appropriate distance between membranes of each type is of paramount importance to minimise the aforementioned negative effects.
Obtaining a magnetic field with sufficient intensity for the correct desalination of the water that is to be processed is difficult with permanent magnets, owing to the complex task of magnetising a hollow cylinder by placing one pole on the external face and another on the internal face. By positioning rolled coils on the external face of the external cylinder and the internal cylinder, a magnetic dipole can be obtained in whose magnetic field the direction of the field lines will be radial between both cylinders. Furthermore, this layout makes it possible to regulate the intensity of said field by controlling the current in the coils. This gives clear benefits in terms of manufacturing costs and the effectiveness of the device.
Other documents describing the closest subject matter provide for a number of more or less complicated features that fail to solve the problem in an efficient and economical way. None of these patents suggest the novel features of the present invention.